1. Field of the Invention
The present invention relates to a planar coil element.
2. Related Background Art
Surface mount-type planar coil elements are conventionally used in various electrical products such as household devices and industrial devices. In particular, small portable devices have come to be required to obtain two or more voltages from a single power source to drive individual devices due to enhanced functions. Therefore, surface mount-type planar coil elements are used also as power sources to satisfy such a requirement.
One of such planar coil elements is disclosed in, for example, Japanese Patent Application Laid-Open (JP-A) No. 2009-9985. The planar coil element disclosed in this document includes an air core coil formed in a spiral shape in a plane and a magnetic sheet stacked on the air core coil and containing an oblate or needle-like soft magnetic metal powder dispersed in a resin material. The above document discloses an embodiment in which the major axes of particles of the soft magnetic metal powder contained in the sheet stacked on the air core coil are oriented in the in-plane direction of the air core coil and the major axes of particles of the soft magnetic metal powder in the magnetic core of the air core coil are oriented in the in-plane direction of the air core coil or in a direction perpendicular to the plane of the air core coil.
However, the above-described planar coil element according to a conventional art has the following problem. That is, when the major axes of particles of the soft magnetic metal powder in the magnetic core of the air core coil are oriented in a direction perpendicular to the plane of the air core coil, the planar coil element is low in strength when subjected to the bending stress of an element-mounting substrate. On the other hand, when the major axes of particles of the soft magnetic metal powder in the magnetic core of the air core coil are oriented in the in-plane direction of the air core coil, the magnetic permeability of the magnetic core is low.